Human bite

Introduction

A human bite occurs as the result of human teeth penetrating skin. This can happen on purpose if someone forcibly bites down on another person’s flesh or it can happen as an accident. Human bites have a high rate of infection.

Symptoms and signs of human bite

The area of the bite will most likely be painful and tender to touch. The bite results in a semi-circular or oval red patch and may have bruising associated with it.2

Human bite in children

Children often have bite wounds as a result of rough play. The wounds are usually located on face, upper arms and trunk. If bite mark has an inter-canine distance of 3 cm or more, consider abuse from an adult.2

Human bite in adolescents

Adolescents typically have closed fist injuries where the teeth have scratched the knuckles. These often present as small lacerations particularly over the third and fourth metacarpophalangeal joints or the proximal interphalangeal joints of the dominant hand.2

Signs of infection

Signs of infection include:1

Fever

Redness

Swelling

Tenderness

Purulent discharge from the wound.

Complications of human bites

Human bites have higher infection risk than animal bite wounds. This is because of the extensive bacterial flora of the human mouth and skin. One study found that in 50 patients that had an infected human bite, on average, four isolates were cultured per wound. Pathogens in human bite wounds included both aerobic and anaerobic bacteria such as:3

Patients with infected bite wounds on initial evaluation need to be sent to hospital for assessment and appropriate therapy.5

Wound care for human bites

Swabs should be taken to aid in antibiotic management, especially if patient is at high risk of methicillin resistant Staphylococcus aureus (MRSA), eg those who have been in hospital recently, drug users, the military and so on.

Wounds need to be elevated to ease swelling and pain.

In closed fist injuries, the hand should be immobilised in a position of maximal length of ligaments.

Human bite wounds are generally left to heal by secondary intention, the main exception is for facial wounds which are handled by plastic surgeons.5

Antibiotics

Even if a bite wound does not look infected, prophylactic oral antibiotics for 3–5 days are recommended, especially if:

The bite wound occurred on the hand or close to a bone or joint

The bite wound was deep

The wound was surgically repaired

It was associated with a crush injury

It occurred in an immunocompromised patient.

If signs of infection are found on follow up, the course of antibiotics can be extended and swabs repeated.5 The agent of choice is amoxicillin-clavulanate. Alternative agents include a combination of an antibiotics with activity against Eikenella corrodens (eg doxycycline) and an antibiotic with anaerobic activity (eg metronidazole).6

Vaccination

Tetanus immune globulin and tetanus toxoid should be offered to patients with less than two primary immunisations. Those without a recent booster (last five years) can be offered the tetanus toxoid alone.5